Speaking of the nutrition and growth of the teeth,[293] Eustachius says that—given the existence of the dental nerves and bloodvessels—it is not difficult to explain how the teeth are nourished, grow, live, and feel. He therefore rejects the opinion of those who held that the teeth of the lower jaw derived their nourishment from the marrow contained within this bone, and that those of the upper jaw received it from a humorous substance similar to marrow, existing in the large cavity of the upper maxillary bone. Against the supporters of this opinion Eustachius raises, among others, the following objections, viz., that the marrow of the inferior jaw does not in any way touch the teeth, so that such a mode of nourishment cannot be imagined, and that it is completely erroneous that the large cavity of the upper maxillary bone contains a humor similar to marrow. This passage of Eustachius’ book gives clear evidence that he was well acquainted with the maxillary sinus, described a century later by the English anatomist, Highmore, who gave it his name. The existence of this cavity was, besides, already known before the time of Eustachius. The author also says that those who believe that the internal cavity of the teeth contains marrow, and that this serves to nourish them, are grossly deceived. In the same chapter, Eustachius confutes an opinion, at that time generally diffused and put forward for the first time by Aristotle, viz., that the teeth grow throughout a whole lifetime. In the senile age, he says, the teeth become impaired still earlier than the other organs. They become thinner by deficiency of nourishment, and, at the same time, discolored; the incisors and canines, as they waste away, come to be also less sharp than they were; and the molars, losing their tubercles or cups, become levelled down and smooth. If, notwithstanding the evident wearing out of the teeth, they seem sometimes to grow longer, this appearance is not to be trusted, for it happens not unfrequently that the teeth appear to have grown longer simply by atrophy of the gums, or also because some humor or other morbid substance pushes them outward. As to the sensibility of the teeth,[294] Eustachius is of the opinion that these organs possess, besides the sensibility to pain, two other species of sensibility; for, following the ideas of Galen, he also holds that the teeth together with the tongue partake in the sense of taste; and he further considers the disagreeable sensation known as _setting on edge of the teeth_, as a species of tactile sensation peculiar to these organs. But in which part of the tooth does the faculty of feeling reside?